Well, that's not the direction I usually travel, so maybe that particular part of Lake Shore is congested without me noticing it. But it strikes me as odd why people just wouldn't use Marine Parade as a detour in that case. I've never seen Marine Parade congested. Anyway, if I don't forget, I'll snap a picture of the intersection tomorrow morning at around 8:15 am. A picture's worth a thousand words after all.
Every time you add a new lane - or a brand-new 400-series highway, for that matter - it only encourages more traffic and more rapid uptake of the newly-added capacity. In very short order you get the "new normal-" which is traffic congestion. The answer lies in some combination of much better public transit, discouragement of personal motor vehicles driven by a single occupant (or at least the encouragement of driverless vehicles which can handle greater vehicular density than vehicles piloted by very fallible, distracted, entirely human drivers who are festering in a stew of road rage, impatience and anxiety) and a slew of other measures. We need to think outside the box and opt for solutions that don't reflexively reflect stale thinking from past eras.
The problem here (and I am speculating a little bit because I don't think there is hard data available) is that the demographics of people who move into Humber Bay tend to consist of households with different commuter patterns. One person may be able to board a streetcar or GO train to their job downtown, but the other person is likely driving to their work in some Mississauga business park. Transit isn't an option in the latter case.
You'd a'thunk that Liberty Vlg developments would have paid for that road alongside rail corridor by now, that Mystic Point weren't to go up without work getting done on Legion Road, yes, etc.!